Method for removing contaminant compounds respectively having benzene ring therein from surface of Si layer and method for producing semiconductor device including step for removing contaminant compounds

ABSTRACT

A method for removing contaminant compounds respectively having a benzene ring therein from the surface of an Si layer, the method containing enter a step for causing the Si layer to contact with the air, oxygen or ozone under a heated condition or a step for causing the Si layer to contact with a mixture of sulfuric acid and hydrogen peroxide or a mixture of pure water and ozone. The method can be applicable to methods for providing a field effect transistor.

FIELD OF THE INVENTION

[0001] This invention relates to methods for removing contaminantcompounds respectively having a benzene ring therein from the surface ofan Si layer and methods for producing semiconductor devices, the methodsrespectively including one or more steps for removing contaminantcompounds respectively having benzene ring therein from the surface ofan Si layer.

BACKGROUND OF THE INVENTION

[0002] The production processes of a semiconductor device are conductedin a clean room, and the semiconductor wafers are frequently washed withpure water, because contaminants such as dusts, mists, and fineparticles composed of conductive compound atoms readily jeopardize theproperty such as the insulation characteristics of the semiconductordevices produced employing the foregoing semiconductor wafers.Unfortunately, however, it is not easy to keep the internal atmosphereof a clean room absolutely clean, and the pure water employed forwashing the semiconductor wafers is gradually contaminated. Exemplarycontaminants jeopardizing the insulation of a gate insulator layer of afield effect transistor having a gate insulated from a channel layerand/or the insulation of a capacitor are phthalic acid ester which isemployed for a draught test of a clean room, dibutyl phthalate which isemployed as a plasticizer employable for producing various plasticvessels, boxes, other apparatus or the like, and butyl hydroxy toluenewhich is employed as a plasticizer employable for producing wafer casesor the like.

[0003] For the purpose to identify the contaminants of a contaminatedsemiconductor wafer before and after a step for producing a gateinsulator layer of a field effect transistor, a wafer-heatinggas-removing gas chromatography mass spectrometer was employed. FIG. 1is a gas chromatogram of a gas evaporated from an Si substrate justafter being washed with pure water and FIG. 2 is a gas chromatogram of agas evaporated from an Si substrate on which a gate insulator layer hasbeen produced. It is well known that the Y axis of a chromatogramrepresents relative strength or detected quantity of a detected compoundand the X axis of a chromatogram represents the time at which theforegoing compound was detected or the mass of the compound detected.

[0004] For the purpose to identify the contaminants remainedunevaporated on an Si water after heating it in N₂ gas for 10 minutes, awafer-heating gas-removing gas chromatography mass spectrometer wasemployed. FIG. 3 is a gas chromatogram of a gas evaporated from an Sisubstrate heated at a temperature range of 500° C. through 700° C. in N₂gas for 10 minutes. Benchtop/PBM search results show the substancesrepresented respectively by A and B shown in FIG. 3 are 1-(phenylthio)-1-(trimethylsilyl)-2-propene and (trimethylsilyl) adamantonerespectively having a molecular construction respectively shown in FIG.4A and in FIG. 4B.

[0005] Results of an analysis applied to FIGS. 1, 2 and 3 are itemizedbelow.

[0006] 1. Major contaminants of an Si wafer under progress of aproduction process for producing a semiconductor device are compoundseach of which has a benzene ring therein.

[0007] 2. A high temperature process conducted for producing a gateinsulator layer is effective to remove some volatile sorts ofcontaminants from the surface of an Si wafer.

[0008] 3. A heating process applied to an Si wafer on which a gateinsulator layer has been produced, the heating process being conductedat a temperature range of 500° C. through 700° C. in N₂ gas for 10minutes, causes silylyzation to occur for reacting with some of thefunctional groups alone of the compounds each of which has a benzenering therein, resultantly converting the compounds to other non-volatilesorts of compounds, such as 1-(phenylthio)-1-(trimethylsilyl)-2-propene, and trimethylsilyl adamantone.

[0009] The above results imply a reaction which cleaves benzene rings ofthe contaminant compounds respectively having benzene rings thereinwould convert the contaminant compounds to volatile compounds which canreadily be removed from the surface of an Si wafer.

[0010] As a matter of fact, since most compounds respectively having abenzene ring therein are conductive, such compound contaminants readilyjeopardize the insulation of an insulator layer located between aconductor layer of a semiconductor device e.g. a gate insulator layer ofa field effect transistor and an insulator layer composing a capacitorproduced in a semiconductor device.

OBJECTS AND SUMMARY OF THE INVENTION

[0011] Accordingly, a first object of this invention is to provide amethod for removing contaminant compounds each of which has one or morebenzene rings therein from the surface of an Si layer.

[0012] A second object of this invention is to provide a method forproducing a field effect transistor, the method including a step forremoving contaminant compounds each of which has one or more benzenerings therein from the surface of an Si layer.

[0013] A third object of this invention is to provide a method forproducing a semiconductor device containing a capacitor producedtherein, the method including a step for removing contaminant compoundseach of which has one or more benzene rings therein from the surface ofan Si layer.

[0014] This invention is based on a concept described below.

[0015] 1. Major contaminants remaining on an Si wafer after a hightemperature process for producing a gate insulator layer arenon-volatile compounds respectively having a benzene ring therein, suchas 1-(phenyl thio)-1-(trimethylsilyl)-2-propene, trimethylsilyladamantone and the like.

[0016] 2. An action to cause an Si wafer having the foregoingcontaminants thereon to contact with a gas such as the air, oxygen andozone under a temperature range of 500° C. through 700° C. or with aliquid such as a mixture of sulfuric acid and hydrogen peroxide and amixture of pure water and ozone causes silylyzation to occur to cleavesome of the benzene rings of the foregoing non-volatile compounds,resultantly converting the non-volatile compounds to chain silyl estersor the like which are volatile.

[0017] Accordingly, a first method for removing contaminants from asurface of an Si layer in accordance with this invention comprises:

[0018] a step for causing the Si layer to contact with a gas selectedfrom a group of the air, oxygen and ozone under a heated condition, forcausing silylyzation to occur for the contaminants to cleave a benzenering of at least one of the contaminants, during a process for producinga semiconductor device.

[0019] It is realistic to conduct the foregoing process during a processfor producing a gate insulator layer of a field effect transistor or aprocess for decompose a silane for depositing an SiO₂ layer on an Silayer.

[0020] A second method for removing contaminants from a surface of an Silayer comprises:

[0021] a step for causing an Si layer to contact with a liquid selectedfrom a group of a mixture of sulfuric acid and hydrogen peroxide and amixture of pure water and ozone for causing silylyzation to occur forthe contaminants to cleave a benzene ring of at least one of thecontaminants, during a process for producing a semiconductor device.

[0022] It is realistic to conduct the foregoing process during a processfor producing a gate insulator layer of a field effect transistor.

[0023] A first method for producing a field effect transistor inaccordance with this invention includes the foregoing first method forremoving contaminants from a surface of an Si layer in accordance withthis invention.

[0024] A second method for producing a field effect transistor inaccordance with this invention includes the foregoing second method forremoving contaminants from a surface of an Si layer in accordance withthis invention

[0025] A first method for producing a semiconductor device containing acapacitor therein in accordance with this invention includes theforegoing first method for removing contaminants from a surface of an Silayer in accordance with this invention.

[0026] A second method for producing a semiconductor device containing acapacitor therein in accordance with this invention includes theforegoing second method for removing contaminants from a surface of anSi layer in accordance with this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] This invention, together with its various features andadvantages, can be readily understood from the following more detaileddescription presented in conjunction with the following drawings, inwhich:

[0028]FIG. 1 is a gas chromatogram of a gas evaporated from an Sisubstrate just after being washed with pure water,

[0029]FIG. 2 is a gas chromatogram of a gas evaporated from an Sisubstrate on which a gate insulator layer is produced,

[0030]FIG. 3 is a gas chromatogram of a gas evaporated from an Sisubstrate charged in a CVD apparatus which is filled with N₂ gas,

[0031]FIGS. 4A and 4B show the results of Benchtop/PBM search foridentifying the substances shown as respectively A and B in FIG. 3,

[0032]FIG. 5 is a cross section of an Si substrate under a progress forproducing a field effect transistor,

[0033]FIG. 6 is a gas chromatogram of a gas evaporated from an Sisubstrate just after being applied with a process for removingcontaminants from a surface of an Si substrate in accordance with thefirst phase of this invention,

[0034]FIG. 7 is a gas chromatogram of a gas evaporated from an Sisubstrate kept in a CVD apparatus which is filled with N₂ gas,

[0035]FIG. 8 is a cross section of an Si substrate under a progress forproducing a field effect transistor in accordance with this invention,

[0036]FIG. 9 is a cross section of a field effect transistor producedemploying a method in accordance with the first and second embodimentsof this invention,

[0037]FIG. 10 is a histogram showing a result of a dielectric strengthtest conducted for field effect transistors produced employing a methodin accordance with the first embodiment of this invention,

[0038]FIG. 11 is a histogram showing a result of a dielectric strengthtest conducted for field effect transistors produced employing Si waferskept in N₂ gas for 10 minutes,

[0039]FIGS. 12A, 12B, and 12C, are respectively a gas chromatogram of agas evaporated from an Si wafer just after being washed with pure water,a gas chromatogram of a gas evaporated from an Si wafer after a gateinsulator layer is produced and a gas chromatogram of a gas evaporatedfrom an Si wafer after a process for causing the Si wafer to contactwith a mixture of sulfuric acid and hydrogen peroxide or a mixture ofpure water and ozone in accordance with the second embodiment of thisinvention.

[0040]FIG. 13 is a histogram showing a result of a dielectric strengthconducted for field effect transistors produced employing a method inaccordance with the second embodiment of this invention,

[0041]FIG. 14 is a histogram showing a result of a dielectric strengthconducted for field effect transistors produced employing Si wafers forwhich the process for removing contaminants from the surface of an Siwafer in accordance with this invention is not conducted.

[0042]FIG. 15 is a cross section of a field effect transistor attachedby a capacitor connected therewith in accordance with the third andfourth embodiments of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] Referring to drawings, methods for respectively producing fieldeffect transistors in accordance with a first and second embodiments ofthis invention and methods for respectively producing field effecttransistors attached by a capacitor connected therewith in accordancewith a third and fourth embodiments of this invention will be describedbelow.

[0044] First Embodiment A method for producing a field effecttransistor, the method containing a step for removing contaminants froma surface of an Si substrate, by causing the Si wafer to contact withthe air, oxygen or ozone at a temperature range of 500° C. through 700°C. preferably under a condition in which a silane is available.

[0045] Referring to FIG. 5, a selective oxidation process is conductedto produce a field insulator layer 2 surrounding active areas in each ofwhich a field effect transistor is scheduled to be produced, on thesurface of an Si substrate 1 containing impurities of one conductivity.After the Si substrate 1 (Hereinafter referred to as an Si wafer undersome situation.) is washed with pure water, a wet oxidation process or apyrogenic oxidation process is conducted to produce a thin SiO₂ layer 3.

[0046] The Si wafer 1 is charged in a CVD furnace in which a lowpressure CVD process is conducted to produce a conductive Si layer 4(See FIG. 8) on the thin SiO₂ layer 3. In the CVD furnace, the Si wafer1 is allowed to contact with a mixture of the air and a silane e.g. SiH₄ at a temperature range of 500° C. through 700° C. for a relativelylong time e.g. 10 min.

[0047] As a result, silylyzation occurs to cleave some of the benzenerings of compounds such as 1-(phenyl thio)-1-(trimethylsilyl)-2-propene,trimethylsilyl adamantone, C₆H₇SC (Si(CH₃)₃) HC₂H₃ or the like,resultantly converting the compounds to 2-piperidinecarborylic acid,1-(trimethylsilyl)-, trimethylsilyl ester, ethanedioic acid, bis(trimethylsilyl) ester, (CH₃)₃ SiOCOC (Si(CH₃)₃) HCOO Si(CH₃)₃, (CH₃)₃Si OCO Si(CH₃)₃ or the like. Since the latters are volatile, thecontaminants are readily removed. FIG. 6 is a gas chromatogram of a gasevaporated from the foregoing Si wafer.

[0048] A gas chromatogram of a gas evaporated from the foregoing Siwafer is shown in FIG. 6. In this specification, a process for removingcontaminant compounds from the surface of an Si layer by causing the Silayer to contact with the air, oxygen or ozone, is defined as a firstphase of this invention.

[0049] For the purpose of comparison, a gas chromatogram of a gasevaporated from an Si wafer kept in a CVD furnace in which N₂ gas isfilled, is shown in FIG. 7.

[0050] Referring to FIG. 8, a CVD process is conducted to produce aconductive Si layer 4 on the thin SiO₂ layer 3.

[0051] Referring to FIG. 9, a piled layer consisting of the conductiveSi layer 4 and the thin SiO₂ layer is patterned into a shape of a gateelectrode. An ion implantation process is conducted to produce a source5 and a drain 6 along the top surface of the Si layer 1. A metal layeris produced to cover the Si wafer and the metal layer is patterned intoshapes of a source electrode 8 and a drain electrode 9.

[0052] A dielectric strength test is conducted for plural specimens ofthe field effect transistor produced in a manner described above.Results of the tests are shown in a histogram shown in FIG. 10. Nearly100% of the specimens show a satisfactory result.

[0053] For the purpose of comparison, plural field effect transistorsare produced employing Si wafers which were kept for a while in a CVDfurnace in which N₂ gas is filled. A gas chromatogram of a gasevaporated from the Si wafer is shown in FIG. 7. A dielectric strengthtest is conducted for the foregoing plural field effect transistorsproduced employing Si wafers which were kept for a while in a CVDfurnace in which N₂ gas is filled. Results of the tests are shown inFIG. 11. It is clear the results are entirely unsatisfactory.

[0054] Plural experiments have been conducted to prove that the processin which an Si wafer is contacted with the air at a temperature range of500° C. through 700° C. preferably in a CVD furnace in which somequantity of a silane may remain, can be replaced by a similar process inwhich an Si wafer is contacted with oxygen or ozone under similarconditions. It is noted that the length of period required for removingthe contaminants is shortened, in each of the foregoing cases. Themagnitude of the time shortening effect is remarkable in the case ofozone. In reality, a period of 5 through 10 minutes is enough for thecase of oxygen and a period of 3 through 5 minutes is enough for thecase of ozone.

[0055] Further, it is proved that the process for removing contaminantcompounds from a surface of an Si layer can be effectively conductedbefore a process for producing a thin SiO₂ layer. In other words, theprocess for removing contaminant compounds from a surface of an Si layercan be conducted either before or after a process for producing aninsulator layer of which the insulation is required to be improved.

[0056] Second Embodiment

[0057] A method for producing a field effect transistor, the methodcontaining a step for removing contaminants from a surface of an Sisubstrate, by causing an Si layer to contact with a mixture of sulfuricacid and hydrogen peroxide or a mixture of pure water and ozone.

[0058] Referring to FIG. 5 again, a selective oxidation process isconducted to produce a field insulator layer 2 surrounding active areasin each of which a field effect transistor is scheduled to be produced,on the surface of an Si substrate 1 containing impurities of oneconductivity. After the Si substrate or the Si wafer 1 is washed withpure water, a wet oxidation process or a pyrogenic oxidation process isconducted to produce a thin SiO₂ layer 3.

[0059] The Si wafer is contacted with a liquid which is a mixture ofsulfuric acid and hydrogen peroxide or a mixture of pure water andozone. As a result, silylyzation occurs to cleave some of the benzenerings of compounds such as 1-(phenyl thio)-1-(trimethylsilyl)-2-propene,trimethylsilyl adamantone, C₆H₇SC (Si(CH₃)₃) HC₂H₃ or the like,resultantly converting the compounds to 2-piperidinecarborylic acid,1-(trimethylsilyl)-, trimethylsilyl ester, ethanedioic acid, bis(trimethylsilyl) ester, (CH₃)₃ SiOCOC (Si(CH₃)₃) HCOO Si(CH₃)₃, (CH₃)₃Si OCO Si(CH₃)₃ or the like. Since the latters are volatile, thecontaminants are readily removed.

[0060] To prove the effect for removing the contaminant compounds from asurface of an Si layer, gas chromatography tests were conductedrespectively for an Si wafer just after being washed with pure water,for an Si wafer after a gate insulator layer is produced and for an Siwafer after a process for causing an Si wafer to contact with a mixtureof sulfuric acid and hydrogen or a mixture of pure water and ozone.

[0061] Referring to FIGS. 12A, B and C, a gas chromatogram of a gasevaporated from the Si wafer just after being washed with pure water isshown in FIG. 12A, a gas chromatogram of a gas evaporated from the Siwafer after a gate insulator layer is produced is shown in FIG. 12B anda gas chromatogram of a gas evaporated from the Si wafer after a processfor causing an Si wafer to contact with a mixture of sulfuric acid andhydrogen peroxide or a mixture of pure water and ozone is shown in FIG.12C. It is clear from FIG. 12C that nearly 100% of the contaminants areremoved by a process specific to this invention.

[0062] Referring again to FIG. 8, a CVD process is conducted to producea conductive Si layer 4 on the thin SiO₂ layer 3.

[0063] Referring to FIG. 9, a piled layer consisting of the conductiveSi layer 4 and the thin SiO₂ layer is patterned into a shape of a gateelectrode. An ion implantation process is conducted to produce a source5 and a drain 6 along the top surface of the Si layer 1. A metal layeris produced to cover the Si wafer and the metal layer is patterned intoshapes of a source electrode 8 and a drain electrode 9.

[0064] In the foregoing manner, a field effect transistor having a gateinsulator layer of which the magnitude of insulation is improved, issuccessfully produced.

[0065] Dielectric strength tests are conducted for a group of fieldeffect transistors produced in the foregoing manner. Results of thetests are shown in a histogram shown in FIG. 13. Nearly 100% of thespecimens show a satisfactory result.

[0066] For the purpose of comparison, a group of field effecttransistors produced employing Si wafers for which the process forremoving contaminants from the surface of an Si wafer in accordance withthis invention is not conduced. Dielectric strength tests are conductedfor the field effect transistors produced employing Si wafers for whichthe process for removing contaminants from the surface of an Si wafer inaccordance with this invention is not conduced. Results of the tests areshown in FIG. 14. It is clear the results are unsatisfactory.

[0067] Plural experiments have been conducted to prove that the processin which an Si wafer is contacted with a mixture of sulfuric acid andhydrogen peroxide or a mixture of pure water and ozone can be conductedeither before or after a process for producing an insulator layer ofwhich the insulation is required to be improved.

[0068] Third Embodiment

[0069] A method for producing a field effect transistor attached by acapacitor connected therewith, the method containing a step for removingcontaminants from a surface of an Si substrate, by causing an Si layerto contact with the air, oxygen or ozone at a temperature range of 500°C. through 700° C. preferably under a condition in which a silane isavailable.

[0070] Referring again to FIGS. 5 and 8, a process similar to that whichwas employed for the first and second embodiments is employed to producea field effect transistor.

[0071] Referring to FIG. 15, after the gate electrode 4 is covered by aninsulator layer 7, a contact hole is produced only for the drain 6. Adoped poly cryslaline Si layer is produced on top of the Si substrate 1,which is patterned into a shape of a first electrode 10 of a capacitor.An SiO₂ layer is produced to cover the first electrode 10, before ametal layer is produced on the entire surface of the Si wafer 1. Themetal layer is patterned to shapes of a source electrode 8 and a secondelectrode 12 of the capacitor.

[0072] When the field effect transistor composes a memory cell having aone transistor one capacitor structure, the second electrode 12 of thecapacitor is grounded, and the gate electrode 4 works as a word line andthe source electrode 8 is connected with a bit line.

[0073] During the foregoing process, a process for causing an Si waferto contact with the air, oxygen or ozone at a temperature range of 500°C. through 700° C. is conducted either before or after the process forproducing an insulator layer 3 or 11, for the purpose to removecontaminants from the surface of the Si wafer. When the process isconducted for producing a gate electrode 4, it is preferable to conductthe process in a CVD furnace which is employed for producing the gateelectrode 4.

[0074] Further, it is proved that the length of period required forremoving contaminants is remarkably shortened, when oxygen particularlyozone is employed rather than the air as the active gas.

[0075] In the foregoing manner, a field effect transistor attached by acapacitor connected therewith having a gate insulator layer and aninsulator layer of the capacitor of which the insulation is improved, issuccessfully produced.

[0076] Results similar to those of the first embodiments of thisinvention have been experimentally proved.

[0077] Fourth Embodiment

[0078] A method for producing a field effect transistor attached by acapacitor connected therewith, the method containing a step for removingcontaminants from a surface of an Si substrate by causing an Si layer tocontact with a mixture of sulfuric acid and hydrogen peroxide or amixture of pure water and ozone.

[0079] Referring to FIG. 5 for the fourth time, a process similar tothat which was employed for the third embodiment is employed to producea field effect transistor attached by a capacitor connected therewith.

[0080] During the foregoing process, a process for causing an Si waferto contact with a mixture of sulfuric acid and hydrogen peroxide or amixture of pure water and ozone, for the purpose to remove contaminantsfrom the surface of the Si wafer. When the process is conducted forproducing a gate electrode 4, it is preferable to conduct the process ina CVD furnace which is employed for producing the gate electrode 4.

[0081] In the foregoing manner, a field effect transistor attached by acapacitor connected therewith having a gate insulator layer and aninsulator layer of the capacitor of which the insulation is improved, issuccessfully produced.

[0082] Results similar to those of the second embodiments of thisinvention have been experimentally proved.

[0083] The foregoing description has clarified that methods for removingcontaminant compounds respectively having a benzene ring therein fromthe surface of an Si layer and methods for producing semiconductordevices, the methods respectively including one or more steps forremoving contaminant compounds respectively having benzene ring thereinfrom the surface of an Si layer, have been successfully provided by thisinvention.

What is claimed is:
 1. A method for removing contaminants from a surfaceof an Si layer comprising: a step for causing said Si layer to contactwith a gas selected from a group of the air, oxygen and ozone under aheated condition, for causing silylyzation to occur for saidcontaminants to cleave a benzene ring of at least one of saidcontaminants, during a process for producing a semiconductor device. 2.A method for removing contaminants from a surface of an Si layer inaccordance with claim 1 , wherein said step for causing said Si layer tocontact with a gas selected from a group of the air, oxygen and ozoneunder a heated condition, for causing silylyzation for said contaminantsto cleave a benzene ring of at least one of said contaminants isconducted in an atmosphere containing a substance containing at leastone Si atom.
 3. A method for removing contaminants from a surface of anSi layer in accordance with claim 1 , wherein a temperature range ofsaid heated condition is 500° C. through 700° C.
 4. A method forremoving contaminants from a surface of an Si layer comprising: a stepfor causing said Si layer to contact with a liquid selected from a groupof a mixture of sulfuric acid and hydrogen peroxide and a mixture ofpure water and ozone for causing silylyzation to occur for saidcontaminants to cleave a benzene ring of at least one of saidcontaminants, during a process for producing a semiconductor device. 5.A method for producing a field effect transistor comprising: a step forremoving contaminants from a surface of an Si layer further comprising:a step for causing said Si layer to contact with a gas selected from agroup of the air, oxygen and ozone under a heated condition, for causingsilylyzation to occur for said contaminants to cleave a benzene ring ofat least one of said contaminants, during a process for producing asemiconductor device.
 6. A method for producing a field effecttransistor in accordance with claim 5 , wherein said step for causingsaid Si layer to contact with a gas selected from a group of the air,oxygen and ozone under a heated condition, for causing silylyzation tooccur for said contaminants to cleave a benzene ring of at least one ofsaid contaminants is conducted in an atmosphere containing a substancecontaining at least one Si atom.
 7. A method for producing a fieldeffect transistor in accordance with claim 5 , wherein a temperaturerange of said heated condition of said step for causing said Si layer tocontact with a gas selected from a group of the air, oxygen and ozone is500° C. through 700° C.
 8. A method for producing a field effecttransistor in accordance with claim 5 , wherein said step for causingsaid Si layer to contact with a gas selected from a group of the air,oxygen and ozone under a heated condition, for causing silylyzation tooccur for said contaminants to cleave a benzene ring of at least one ofsaid contaminants is conducted before and/or after a step for producinga gate insulator layer.
 9. A method for producing a field effecttransistor comprising: a step for causing said Si layer to contact witha liquid selected from a group of a mixture of sulfuric acid andhydrogen peroxide and a mixture of pure water and ozone for causingsilylyzation to occur for said contaminants to cleave a benzene ring ofat least one of said contaminants, during a process for producing asemiconductor device.
 10. A method for producing a field effecttransistor in accordance with claim 9 , wherein said step for causingsaid Si layer to contact with a liquid selected from a group of amixture of sulfuric acid and hydrogen peroxide and a mixture of purewater and ozone is conducted before and/or after a step for producing agate insulator layer.
 11. A method for producing a semiconductor devicecontaining a capacitor therein comprising: a step for causing said Silayer to contact with a gas selected from a group of the air, oxygen andozone under a heated condition, for causing silylyzation to occur forsaid contaminants to cleave a benzene ring of at least one of saidcontaminants, during a process for producing a semiconductor device. 12.A method for producing a semiconductor device containing a capacitortherein in accordance with claim 11 , wherein said step for causing saidSi layer to contact with a gas selected from a group of the air, oxygenand ozone under a heated condition, for causing silylyzation to occurfor said contaminants to cleave a benzene ring of at least one of saidcontaminants is conducted in an atmosphere containing a substancecontaining at least one Si atom.
 13. A method for producing asemiconductor device containing a capacitor therein in accordance withclaim 11 , wherein a temperature range of said heated condition of saidstep for causing said Si layer to contact with a gas selected from agroup of the air, oxygen and ozone is 500° C. through 700° C.
 14. Amethod for producing a semiconductor device containing a capacitortherein in accordance with claim 11 , wherein said step for causing saidSi layer to contact with a gas selected from a group of the air, oxygenand ozone under a heated condition, for causing silylyzation to occurfor said contaminants to cleave a benzene ring of at least one of saidcontaminants is conducted before and/or after a step for producing agate insulator layer.
 15. A method for producing a semiconductor devicecontaining a capacitor therein comprising: a step for causing said Silayer to contact with a liquid selected from a group of a mixture ofsulfuric acid and hydrogen peroxide and a mixture of pure water andozone.
 16. A method for producing a semiconductor device containing acapacitor therein in accordance with claim 15 , wherein said step forcausing said Si layer to contact with a liquid selected from a group ofa mixture of sulfuric acid and hydrogen peroxide and a mixture of purewater and ozone is conducted before and/or after a step for producing agate insulator layer.